Experience with Smoke System

Excuse my English! (I’m French)
I spend a lot of time on forum, searching for smoke system for small engine (.40) and I found nothing. I would something easy to install, tune and a lot of smoke. On big engine like gas, it’s easy (more than a small), but with a small engine there are many problems…. Like not enough heat, the smallest pump delivered too much oil, market smoke injector to big….

I decide to equip my Hangar 9 Arrestee .40 plane with a smoke system. Just for the fun. I fly this plane 1 year without, with different prop, must of time with a 10X7 for speed on 30% nitro gas. I prefer speed to pattern...
Now I equip it with a 12.75X3.25 prop and add my smoke system in it. All modification add 1.2 pound to the plane (oil tank, tubing, pump, extra batteries, muffler modification) Ready to fly weight is 7 pound now! But with this prop, this not a problem!

Firt, I install everything like the pump manual explains.... I only put a smoke injector on the muffler. Result.... Bad! Not enough smoke, the pump running to its minimal rate delivered to much oil... not enough restriction on the injector, and the oil arrive in the muffler to cold.

The second version, I install 12" copper tubing in the muffler to preheat the oil and make the output hole very small. I squeeze the end of the tubing with pliers... to reduce the amount of oil and mount the pressure in the oil line. Yes the pump speed can be reduce or increase by the transmitter, but at minimum speed, it still delivered too much oil. But it's working better. Now I can tell I have a smoke system, but not suffisant for the time I spend to install the system. The 4oz oil tank takes 3 minutes to be empty...

But I was not satisfied enough. I need to preheat the oil more, and I need to increase the pressure in the line to make possible to increase or decrease by the transmitter the pump speed.

I make a third version! (time to loose!). I buy a 36" copper tubing and make a lot of spiral with it. I squeeze the last inch of the tubing with pliers to be sure it takes a lot of pressure to make the oil come out. The pump I’m using is very powerful!
I try my new setup yesterday... Not bad, but it could be better. Too much oil... when the pump and all the tubing are primed, I need to reduce the pump rate to minimal... TOO MUCH OIL! It takes 5 minutes to empty the oil tanks and it supposes to take about 8 to 9 minutes when everything is tune perfectly.

The only thing is missing on my system is a regulation valve on the output line. I already buy it, and plan to test it next weekend....

To be continued… If somebody already install and test a smoke system on a small engine like .46 and less…. Let me know!

Images

I experimented with smoke systems on 2 stroke glow engines but I concluded that there was not enough heat in the exhaust system to get enough smoke to see against anything but the bluest sky. You seem to have had more success than me. I have talked to other modellers that have achieved better smoke than me and it is down to having enough heat in the smoke fuel before it is injected into the exhaust system. 4 strokes have hotter exhausts than 2 strokes and gassoline engines are hotter than methanol engines.
With your set-up, you may get better pre-heating if you lag the outside of your exhaust with glass fibre woven tape and increase the length of the pipe up to about 3 m long.
I am also told that exactly where the smoke fuel is injected into the exhaust is also critical, closer to the cylinder is better but it may choke the engine at low revs. It's a good idea to have a switch that automatically turns off the pump at low throttle to prevent the engine quitting.
I had a crude system with no pre-heat on a 60cc gas engine which worked quite well but the diesel I used as a smoke fuel got into everything, it soaked the wooden fuselage and nearly ruined the airframe of my Ohio 28% scale Extra so I removed it. The system used about a litre of smoke fuel in a 10 minute flight, without it on all the time. To throttle the fuel I used a clamp on the flexible line to act as a restrictor, although on my 2 stroke experiments, I used a needle valve from an old engine.

Thanks for your recommendations, but I already try everything to maximize my chance to get smoke…

To get my engine hotter I use now 10% of nitro instead of 30%. I made a small deflector with aluminum fold to deflect the air coming from the prop (not install now, but for the next test it will be there. I will mount it on the muffler (probably increase the temp a lot).

The smoke injector sprays 2 or 3mm from the exhaust of the engine. I have a computer radio, I already install the pump on the gear channel. I can switch it On and Off by a switch and I mix the throttle with the gear to be sure there is no possibilities to start the pump before reaching at least half throttle.

The only think is missing right now: install my deflector on the muffler, install a needle valve on the output line to reduce the flow.

Many people told me to install my copper tubing around head engine, I try it also.... to much vibration and noise coming from the copper tubing and not enough efficient to install this permanently.

Next test, this week-end... I will post the result.... If I can't have better result I will remove it and wait to install it on a bigger power plan.

Nexa,
What smoke fuel are you using, Diesel is the best that is easy to come by but other concoctions people have used contain things like bee's wax. The full-size world uses special light turbine oil but you have to buy this by the drum.

......This oil doesn't smell and it`s not volatile, a must if I want to keep my airplane in my appartement and in the same way my girlfriend!

It's either that or get the GF to accept you just as you are. I was in the GF shopping stage a couple of years ago. One of the things that I made sure to mention is that my home is full of airplanes. That and I park my motorcycle in the front room so it doesn't get stolen (I know, great neighborhood huh). Afterall, I've had it for 28 yrs. If the gals didn't like that, they didn't get too much of my time. I finally came upon one that accepts me exactly as I am.

Finaly.... I crash it... I will repair it.... next winter
But it was smoking a lot (smoke system revision 4!). My system was perfectly tune, and was smoking more than a 1/4 Funtana with is 100cc gas engine with the same smoke system as me. But not tune perfectly.

The key... just enough oil (not to much, not to lean). The oil need to be preheat and the engine hot enought. I use Willcat 10% nitro to keep it hot.

To resume, a .46 engine, can smoke a lot, not more than a gas engine, but closely. But it takes twice as time to clean the airframe after.... real mess.

See the video on the first post.... It was the Version 3!. I finally got a very dense and white smoke on version 4... I just add a needle valve to perfectly tune the oil flow, to be sure every thing was burn in the muffler.